Troubleshooting Left Blinker/Stop Light Not Working on a Trailer

Question:

I purchased this trailer light wiring connector for my 2012 Forester from you about 2 years ago. No problems installing, worked fine, very minimal use since, maybe hooked up 10 times total on a small utility trailer. Now the left turn signal and left brake light do not come on. All other lights work fine - running lights to both sides and right blinker/brake. Any suggestions? Thanks.

asked by: Dave K

Expert Reply:

It really sounds like the ground is not making good enough contact on the left turn signal/tail light and because of that it is able to draw enough amperage to illuminate the blinker function of your bulb. You should check and make sure its grounding to a clean metal surface. A lot of light assemblies ground through the mounting hardware so you will need to make sure its attached to a clean metal surface.

There is a chance the converter box of your setup could be wrong, in order to test that you will need to test for voltage coming into the box and then for voltage coming out of the box with circuit tester like part # PTW2993. If you find that there is voltage going into the box on the left turn signal circuit but not voltage coming out of the box then the box is bad.

If there is not turn signal voltage coming into the box either then you know the problem lies further up on the circuit and you should continue testing for voltage further and further up the circuit until you identify where the problem area is and then fix as necessary.

I attached an FAQ article on trailer wiring and troubleshooting 4-way installs for you to check out also.

expert reply by: Jameson C